Traffic-control system for radio broadcast distribution



June s. 1928. 1,672,372

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UNITED STATES PATENT OFFICE.

EDWARD E. CLEMENT, OF WASHINGTON, DISTRICT OF COLUMBIA, ASSIGNOR TOEDWARD F. COLLADAY, OF WASHINGTON, DISTRICT OF COLUMBIA.

TRAFFIC-CONTROL SYSTEM FOR RADIO BROADCAST DISTRIBUTION.

Application filed. October 28, 1924. Serial No. 746,358.

My invention relates to systems of radio broadcast distribution, and hasfor its object the provision of such a system in which the broadcastedmatter may be relayed through one or several relay stations without lossin quality and to selected subscribers receivlng stations under localcentralized supervision and control of the reception, or of both relaytransmission and reception.

A further object of the invention is to provide a system of broadcastdistribution in which the necessary receiving apparatus is simplifiedboth in structure and operation by the provision of receiving deviceshaving complementary parts at the receiving stations and at acentralized station common to a group of receiving stations therebyreducing the amount of apparatus necessary at the receiving station andplacing an important portion thereof at the central sta tion forsupervision and control by expert operators.

A further object of the invention is to provide a system of radiodistribution and reception in which the receiving apparatus is situatedpartly at receiving stations and partly at a central station common to agroup of receiving stations, the parts at the central station beingarranged to be interchangeably associated with the parts at thedifferent receiving stations.

Various other objects of my invention will be apparent from a perusal ofthe following specification and the drawings accompanying the same.

My invention is illustrated in the accom- 'panying drawings, in which:

Fig. 1 is a geographical diagram of the area of the United Statesdivided with respect to standard time, showing stations positioned toform part of a typical distributing system embodying this invention.

Fig. 2 is an enlarged geographical diagram of a portion of Fig. 1showing subdivision of distribution in localized or districted areas.

Fig. 3 is a diagram showing the subscribers double detector receivingset divided into two single demodulating units, one 10- catcd at thesubscribers station and the other located at the central office, thefirst detector being at the subscribers station and sending long wavesthrough the subscribers line to the second detector at central, whichsends back audio waves to the subscribers telephone.

Fig. 4 is a diagram showing a modification of the circuit of Fig. 3, inwhich regeneration is added, at the subscribers station, and theintermediate wave line coupling at central is included in the cordcircuit.

Fig. 4* is a diagram of a further modification showing the said cordcircuit provided with the same elements as in Fig. 4 except the batterywhich is in two units, one for talking and telephone signaling, and theother for the detector tube plate circuit.

Fig. 5 is a schematic diagram showing the relation of units of any typeconnected up to perform the functions of the circuits shown in Figs. 3,4, and 4.

Fig. 6 is a circuit diagram of double modulating apparatus.

Fig. 7 is a circuit diagram of relay apparatus for stations B or C.

Fig. 8 is a circuit diagram showing means primarily intended for A and Bstations, but which may be located also at C stations, for picking upany single modulated carrier wave which it is desired to put out in thesystem, and changing this into a double modulated wave b heterodyning,amplifying, and transmitting the modulated intermediate frequencycarrier or beat, on a short carrier wave whose frequency is the mean ofthe frequencies of the original carrier and the heterodyning oscillatorwaves.

Fig. 9 is a circuit diagram similar to Fig. 8 showing a modified form ofapparatus that may be used in Fig. 8, employing the autodyne principlefor receiving instead of a double tube heterodyne circuit.

Fig. 10 is a circuit diagram showing equipment supposed to be located atthe A, B, and C stations, for receiving on any single modulated carrierwave, heterodyning and detecting the same and modulating the beat takentherefrom on to the standard frequency short carrier Wave of the nextsucceeding order of stations. If located at station A, the beat would bemodulated and transmitted on the B frequency, and if located at astation B, transmission would then be on standard carrier wave C.

Referring to the drawings, and particularly to Fig. 1, this is a diagramof the United States of America, divided by lines 2%, t, and t into fourdivisions marked resions.

spectively Eastern standard time, Gen

tral time, Mountain time, and Pacific coast time. It happens that thetown of Hutchinson, Kansas, is within fifty miles of the geographicalcenter of the United States and hence I have shown this town with threerings around it, and the letter A, indicating the location either of theheadquarters or master station of the entire system. In each divisionthere is one station with two rings around it, and marked B. These arethe head or master district stations of the several divisions, whichunder certain conditions serve as relay stations between the A stationsand the other B stations for their respective divisions. Other stationsare shown in each division with one ring each, and marked B. These aredistrict stations, and receive either directly from the A stations or onoccasion by relaying from the head or master B stations in theirrespective divi- This illustrates the general manner of distribution,and will be referred to hereinafter.

Fig. 2 shows on an enlarged scale a portion of the eastern standard timedivision, which may be regarded as one or more districts, as it containsa number of district stations B. The main function of this fi 'ure is toshow the relation between the district station and the local or regionaldistributing centers C. It is to be noted that VVashington, D. (1., isthe head or master B station in the eastern division, while other townsfrom Boston to Augusta are shown in Fig. 2 with one ring as ordinarydistributing centers each serving a number (which in practice would bevery considerable) of outlyin local or regional exchange centers markedAround each of these local stations or centers C are groupedsubscribers.

In Fig. 1, I have shown eight district stations B in the easterndivision, ten in the central division, and six each in the mountain andPacific coast divisions, or a total of thirty. This of course isillustrative only and not to be taken as final either in positioning ornumerical selection. As a matter of fact if the area of the UnitedStates be divided up into substantially equal districts, approximatelyone hundred district stations B would be a convenient number, but it isdoubtful whether the trafiic would re uire this many district stationsat first. In ig. 2 I have shown a larger number of stations in part ofthe same territory, or B stations, and have related a considerablenumber of C stations thereto. The location of these is a matter ofchoice, and they may or may not be associated with local telephoneexchanges, as convenience and traffic conditions may demand.

For the purposes of a basic description herein of the system as a whole,in the simplest form, I shall assume that each of the three orders ofstations, B, C, and D, is allotted a single carrier wave frequency forreceiving, which is common to all the stations of the same order, andthat say ten intermediate or long wave frequencies may be modulatedthereon, each intermediate frequency being in turn modulated at audiofrequencies intended for distribution. At certain times these tenintermediate frequencies may all be used at the master station A andbroadcasted on the B carrier wave to all the B stations, which in turnwill demodulate the initial carrier, amplify and reimpose the sameintermediate frequencies and modulations on the common C carrier waveand so relay them to all the C stations, which in turn will demodulatethe carrier waves received by them and reimpose the same upon the commoncarrier wave allotted to all the D or subscribers stations. At othertimes there may be only one or two or even none of the intermediatefrequencies in use by station A and at such times the unusedintermediate frequencies may be allotted to different B stations or evento C stations for local or district broadcasting.

In the first instance, it will be observed that the original modulationson all the intermediate frequencies are simply passed along by relayinguntil they reach the subscribers, who receive them in the originalpackage, so to speak, so that it is entirely possible to say truthfullyto the subscribers that they receive and actually hear the originalaudio modulations, with equal efficiency from all points, foreign ordomestic; and this in spite of the simplicity of their instruments.

Fig. 2 shows geographically the method of distribution in the districtor B areas and the relation in general between B and C stations.

Referring to Fig. 3, the subscribers station A is equipped with aradiophone receiving device including an antenna circuit 28, tuned asusual, and coupled by means of coils 29 to the input side or gridcircuit 125126 of the detector tube 85. The input circuit may be tunedby means of condenser 129, but it is to be understood that thiscondenser and also the tuning elements in the antenna circuit may beadjusted once for all if the subscribers all work on a constantfrequency, as hereinbefore set forth. The plate circuit 127128 of thetube includes one winding 123 of a tuned filter coupler, the other sideof which 121 is connected to extensions 18 and 19 of the subscriberstelephone line circuit 1819. The coil 123 is shunted by a condenser 124,and the capacity and inductance are so adjusted that the short circuitthus formed is resonant to the intermediate frequency waves imposed onthe short carrier waves reaching the subscribers instrument through theantenna 28. The variable condenser 122 is included in series with thecoil 121, because of. the line connection, tuning of the line beingaccomplished at both ends as will presently appear.

At the central office, the line wires 18-19 are connected to any desirednumber of answering and multiple jacks typified by the single jack J,and is provided with extensions 18 -19*'- passing to the radiodepartment or radio switchboard R in the upper part of the figure. Thetelephone jacks are intended to be interconnected with other jacks fortelephonic purposes through a standard cord circuit 2021, 22-23, havingterminal plugs P-P, and bridged by a common talking and signalingbattery B, feeding through the two halves of repeating coil I and alsofeeding through a ring on each plug and test thimble on each jack to thecut off relay circuit 19, so that whenever a plug is in a jack of theline 18--19, circuit from battery to the cut off relay L will becompleted and the line relay L with its connection to the main battery Bwill be cut off and removed entirely from the line. In this cut offportion of the cord circuit are inserted supervisory lamp signals, ss,adapted to be shunted by contacts controlled by supervisory relaysincluded in the conductors 22-23, respectively. These relays respond tocurrent in the subscribers lines when they are interconnected, and thelamps light when the subscribers hang up their receivers.

On the radio switchboard R, the same line is provided with jackstypified by jacks J "J. As shown, these are in pairs, for convenienceonly, and to avoid putting a large number of contacts in one jack. Theupper jack J is a duplicate of the telephone jack J, and has itscontacts connected in parallel to the same conductors, respectively.Jack J is a radio jack pure and simple, and is connected to the sameline wires 18"19 through a tuned filter coupler composed of coils 115and 117 and condensers 116 and 118. The elements 115 and 116 areemployed in conjunction with the elements 121122 at the subscribersstation to tune the line circuit to resonance at the frequency of thelong waves sent forward as demodulated by the subscriber. The elements116117 at central are included in this figure between the line and thejack because by this means the tuning of the line can be made constantand adjusted once for all. The cord circuit adapted to cooperate withthese'twin jacks has corresponding twin plugs P P preferably connectedmechanically so they can be inserted and removed from the jacks at thesame time. The plug P is the terminal of a standard talking circuit90-91, with battery B bridged across it through coils 9293, and providedwith supervisory lamp 101, the controlling shunt therefor 102, thesupervisory relay 103 and the talking shunt therefor 104, also withspecial test coil 106 supplied with a radio tone test through wire 108from the commutator 107. lVhen this plug is inserted in the jack J thecut off relay L of the telephone line is pulled up and the line clearedof all telephone switchboard connection, for radio use.

The plug P forms the terminal of a radio detector circuit, the tip andsleeve of the plug being connected through conductors 9697 with the gridand the filament re spectively of the detector tube 86. The platecircuit 9798 of this tube is connected to the outside terminals of'coils 94 95 which with the bridged coil 92-93 form the usual repeatingcoil connection between two ends of the standard bridged battery cordcircuit. The battery B bridged between the windings 9%95, has itspositive terminal connected to the plate through coil 94 and wire 98,and the conductors 9798 are bridged by a conductor 99 containing aby-pass condenser 100.

The result of this arrangement is as follows: The subscriber calls forradio service by mot-ing his switchhook at station A, up and downrapidly. This flashes the line lamp before the telephone operator, whotransfers the line over an order trunk to the radio operator, whothereupon inserts the twin plugs P into the jacks J J This pulls up thecut off relay L clears the line through from the substation to the cordcircuit 90-91, 9697, and thereupon, assuming that the subscriber hasclosed his filament circuit at the substation, radio waves received onhis antenna 28 are demodulated, and their long wave or intermediatefrequency component, carrying the audio modulations, is transmitted toline through the filter coupler 121-123. From line it passes through thefilter coupler 115- 117 and through the wires 9697 to the grid circuitof the tube 86. The varying potentials thus produced in the grid circuitof the tube are reproduced in current changes in the circuit9795B--94-98. The superaudio frequency waves are absorbed by the circuit99 and the condenser 100, and pure audio frequency waves are propagatedthrough the repeating coil 9495-9293, into the telephone line circuit,through the plug P, the jack J multiple wires 18 19 and line circuit1819. At the subscribers station these audio waves may be received onhis ordinary telephone receiver a, or upon any special form of receiverdesired.

Referring now to Fig. 4, I have shown therein a modification of thecircuit of Fig. 3, in which the following features are introduced:First, I provide a feed back coil or tickler 130 at the subscribersstation; a special receiving telephone 133 with a terminal plug 132adapted to be inserted in the jack 131 bridged across the telephone lineoutside of the filter coupler 121-423; and lastly I have removed thecentral office filter coupler 115-117 from its position between the lineand the jack J as in Fig. 3 and instead thereof have located thiscoupler in a bridge of the cord circuit 9697, thus doing away with thetwin plug P and its connections. This also reduces the number ofcouplers required, and most important of all enables the complete radiocord circuit to be used with any ordinary telephone jack, since theterminal plug P is an ordinary telephone terminal plug. For the reasonstated, I have designated both jacks in this figure by the letter J, thelower one being at the telephone switchboard and the upper one at theradio switchboard. Both may be used interchangeably, or an ordinarytelephone switchboard may be used for radio purposes without any changeother than adding the filter coupler, the detector tube, and otherconnections to an ordinary standard answering plug cord. Thisinterchangeability of the parts, makes it possible to give radio serviceon any telephone switchboard, using the same operators if desired, forboth services. It also makes it possible to lengthen the life of atelephone switchboard, by rewiring the cords and converting it into aradio switchboard.

In Fig. 4, the antenna circuit 28 and the coupler 29 are the same asbefore; the grid circuit is 125126, the plate circuit 127-128 includes atickler coil 130, and the other parts have been referred to. At thecentral station the plug P is connected as in Fig. 3 to the repeatingcoil, battery, supervisory lamp, controlling relay therefor, tone test,etc. The coil 115 of the central office filter coupler is bridged acrossthe terminals of the plug, with its tuning condenser 116. The twinmember of the filter coupler 117, with its shunting tuning condenser118, is

.bridged through conductors 9697 across the grid circuit terminals ofthe tube 86. The plate circuit 9T-98 is connected to the repeating coilin the cord, and in this case also includes a tickler coil 134, whichmay be cut in and out of the plate circuit at will by means of a switch98. This coil 134 feeds back into the grid circuit waves at intermediatefrequency, as received over the line, and is intended to give a higherratio of amplification in the audio current returned to the subscriberthan would be possible with out it. It should be noted however, thatinstead of thus using the regenerative principle, I contemplateemploying radio and audio amplification in one or more stages of each,inserted between the detector tube 86 and the plug P or P. (Fig. 4.)

In Fig. 4 I have shown a modification of the cord circuit in Fig. 4,which consists in providing a separate battery B for the plate circuit97-98 of the tube. This battery is located next to the plate, and thebypass condenser 100 is bridged across the ter minals of the repeatingcoils 94-95. This approaches more nearly to the common or standardmethod of connecting circuits than the bridge circuit of Figs. 3-4, andwhile probably not more efficient, is a little more flexible, as itpermits the voltage of the B battery to be varied at will, withoutreference to the Voltage of the battery B which according to telephonepractice is constant at about 22 volts. Thus, if amplifier tubes areused between the tube 86 and the coils 94-95, a separate plate batterywould be required for the amplifiers, giving a higher voltage accordingto common practice. The operation of Figs. 4-4 is as follows: Thesubscriber may call as before and in response to his call the radiooperator gives him a cord circuit with terminal plug P or P, whereuponhis unit through the detector tube 85 demodulates the short wave carrierreceived on antenna circuit 28, and sends the intermediate or long wavemodulation thereof through the line wires to central, where it passes tothe jack J and the plug P and is repeated by the tuned filter coupler115- 117 into the grid circuit 9697 of the tube 86. Through this tube,and any amplifying tubes which may be employed, the audio modulationsare first detected and then amplified and sent back through therepeating coil to the plug P and the jack J to the subscribers line. Atthe subscribers station they are received either on his regulartelephone receiver, or on the special telephone 133 which typifies anykind of receiver which it may be found expedient and desirable toemploy.

I contemplate dividing the cord circuits shown in Figs. 3, 4, 4, inclasses, the first class being like those shown herein, without anyamplification; the second class having suliicient audio amplification orradio ampli fication, or both, to insure good operation of thesubscribers table talker; and those of higher classes having moreamplification, serving for the operation of loud speakers giving varyingvolumes of sound. Thus it may be stated that a No. 1 cord circuit wouldbe as shown, with only one detector tube and the subscriber wouldtherefor receive his audio message on a head telephone or on hisordinary telephone receiver held to his ear; with a N0. 2 set at centralthere would be one stage of audio amplification sufiicient at thesubscriber's station for a table talker which would not annoy theneighbors; a No. 3 set would have sufficient amplification to actuate areasonably loud speaker, while a No. 4 set might be so equipped as tofill a hall. For different classes of service as thus outlined,

the subscriber should be charged different rates, as in long distancetelephone service. It is very necessary that there be metering uponwhich to base the charges, since the service is a time service and not amessage service. For this purpose I contemplate including in each cord adistinctive type of meter actuator which will operate the subscribersline meter which may be his telephone meter or a separate meter asdesired, a number of times per hour determined by the class of servicehe is receiving. Thus the No. 1 cord circuit may be connected to acommutator that closes the line meter circuit once every hour; No. 2 mayhave a meter actuator that works twice every hour; No. 3 may have anactuator that works three times in the hour; while No. 4 may have itsactuator work every ten or twelve minutes. The reason for selectingthese time divisions is that the average charge per message fortelephone service is about five cents. At five cents per hour, andaveraging three hours service per day, a subscribers radio bill would be$4.50 per month. This is fairly comparable to the earnings of an averageresidence telephone for the same period, on a message rate basis. Thefractions of time could not be out below a five cent value, unless aseparate radio meter be provided for each line and it is desired toavoid this expense, as well as the upkeep of one hundred per cent ofadditional meters. In Patent 1,522,359, issued January 6, 1925, I haveshown and described a metering system which is suitable for use with thesystem of circuits herein disclosed. I have disclosed and shall claimthe adaptation of this metering circuit to the present system.

It should be particularly noted, that a subscriber, (which term is meantto include any user) may not keep his radiophone in service a full hour,a pertinent example being that of a man who desires to obtain a baseballscore or other special information. A special provision should be madefor registering such service, as it involves all the elements of expenseto the operating company which would be included in a much longerconnection. For this purpose the operator may have a push button 9connecting the actuating generator G direct to the meter circuit throughthe plug P, as shown in one form in Fig. 3, together with the automaticactuating means for the meter, comprising the commutator g which atstated intervals connects the generator G to the wire 297 leading to thethird contact on the plug P, which when the plug is inserted in jack Jcornpletes the circuit from wire 297 through wire 298 to the cut offrelay wire 19", thence to the high winding 299 of the meter LM In Fig.3, the meter is shown as the ordlnary standard telephone line meter,which would thus serve a double purpose, registering both the telephonecalls and also the time of radiophone use in terms of telephone callunits or telephone message units. Such a meter by reason of the highresistance in its winding 299 will not respond to the battery currentwhich energizes the cut off relay L but when the operator connects agenerator as G producing current of higher voltage, then the metermagnet becomes sufficiently energized to attract its armature and closethe circuit of its low winding 300, the rush of current through the lowwinding producing strong and certain actuation of the meter countingdevice 301.

By thus having the operator always press the keys 9 immediately aftermaking a radio phone connection, there will always be made a base chargeof one telephone message unit for the connection. If it should happenthat the commutator close the actuating circuit immediately afterward,the meter would register two units for the first hour of use. If itshould happen that the subscriber hangs up in fifteen minutes the linewould still bear the charge of two units for one hour. On the otherhand, if the connection was made immediately after the commutator hadclosed the metering circuit, then no addi tional charge would be madefor an hour,

and if the subscriber should hang up within less than an hour, he wouldhave only the one charge against the line. In any event, the chargewould be safe to the company and fair to the subscriber as all publicservice corporations make a service charge if the measured rate chargedis below a minimum amount. A commutator individual to each cord startedwhen the cord is connected would of course register individual time useonly.

Referring to Fig. 5, this is a schematic diagram showing without detailthe layout of the subscribers line instruments and the central ofiiceradio connections just described and illustrated in Figs. 3, 4, and 4:.Line wires shown at 1819 extend from the subscribers station A to thecentral office where they terminate on a jack J. As the units of theapparatus are marked with legends specific description is unnecessary.The principal point is that no hysical connection with the telephoneline 1s made at either end except through a tuned filter coupler passingonly superaudio frequencies.

Fig. 6 illustrates an arrangement of apparatus and circuits for producmgdouble modulation of a primary or short carrier wave, that is to say, tomodulate a relatively long wave carrier, and then modulate this longwave upon a relatively short wave carrier which may conveniently beradiated in the usual fashion. Means for receiving and demodulating suchdouble modulated waves have been described in connection with Figs. 3,4, and 4 In Fig. 6, 150 is a microphone transmitter in a local circuit151 supplied with energy by battery B and containing the primary windingof an induction coil 152, the secondary of which is connected in thegrid circuit 153 of the modulator tube 154. said circuit containing abattery B The plate circuit 155-156 of the tube 154 is bridged by thepower battery 13 and choke coils 157. and is connected through radiojack coil 157, to the plate of the long wave oscillator tube 158. Thegrid circuit of the tube 158 contains a battery B is differentiallyconnected to one coil of the coupler 161, which in turn has a wireconnection 160 back to the plate circuit. The coupler 161 is tuned onits input side to the long wave frequency supplied by the tube 158, andits secondary winding is connected to the grid circuit of a secondmodulator tube 162, containing a battery B The plate circuit of the tube162 is bridged by power battery B and choke coil 163, and is connectedthrough the radio choke coil 163 to the plate of the short waveoscillator tube 164. The grid circuit of this tube 164 con tains abattery 13 and is connected through a condenser 167 and wire 167 to theantenna circuit, which is also connected back to the plate circuitthrough wire 166. The antenna circuit 57 is thus supplied with shortwave oscillations modulated by the tube 162 with long wave oscillationswhich in turn have been modulated by the tube 154 with audio modulationsdue to the primary modulator or microphone transmitter 150. It should benoted that this circuit is an adaptation of the Heising modulatorcircuit in common use, and it is not claimed herein, being shown forexample on page 682 of the work on Principles of Radio Communication byJ. H. Morecroft. published by John Viley & Sons, New York, 1921. The useof this apparatus however in combination with other elements to producethe results stated, and the adaptation of the circuit in question to thepurposes of this system, are novel and will be claimed herein.

The apparatus of Fig. 7 is intended to receive a double modulatedcarrier wave such as that radiated from the antenna in Fig. 6,demodulate the same and reimpose the long wave or intermediatefrequency, with its modulations. upon another short wave carrier whichis the carrier wave allotted to stations C or the subscribers stationsD, according as to whether the apparatus is situated at a B or a Cstation, respectively. The purpose of this is to transmit from the pointof origin to the point of destination the same intermediate long wavecarrier with the same audio modulations intact and merely passed alongby relaying from station to station on short carrier waves.

The apparatus and circuits of Fig. 7 is the same at both the B and Cstations except that the transmitted or short primary carrier waves aredifferent. to enable reception and transmission to be effected atdifferent wave lengths or frequencies.

Referring to Fig. 7 in detail, 54 is the receiving antenna coupled at 174 t0 the grid circuit of the detector 170, whose plate circuit isconnected through a tuned filter coupler 175 to the grid circuit of theamplifier tube 171. whose plate circuit is connected through thetransformer 176 to the grid circuit of the modulator tube 172, which inturn has the usual Heising connections 178-179 to the circuit of theoscillator tube 173; the radio choke coil 178, the power battery B andthe magnetic choke coil 177 being arranged as usual. The grid and plateof the oscillator tube 173 are connected to the antenna inductance coil180, which with the usual tuning condenser 186 is included in theantenna circuit 55. Filament batteries B, B, and B and plate batteries13 and B are located as usual. As thus described, the assemblageconstitutes a relay set which will take in the modulated long waves on ashort wave carrier, and retransmit them on a carrier of differentfrequency, without demodulating or disturbing the modulations of theintermediate or long wave.

Another arrangement. of apparatus and circuits for performing thefunctions of the arrangement of Fig. 7, that is to relay by doublemodulation, carrying the same audio modulations. is shown in Figs. 8 and9. Referring to Fig. 8, 185 is the receiving antenna with coupler 186connecting it to the detector tube 181 which has a triple coiloscillator coupler 187, 182 being the oscillator for producing localheterodyning waves. The detector circuit and the oscillator circuit areconnected to the tuned filter coupler 188, the output side of which isconnected to the grid circuit of the amplifier tube 183, the platecircuit of which is in turn connected through a tuned radio frequencytransformer to the grid circuit of the amplifying tube 184, the platecircuit of which goes to the antenna 191. B is the plate battery of theoscillator and the first tube 181, which, while I have called it adetector because it occupies that position, may be regarded rather as anamplifying tube. since it is worked by preference on the straight.portion of the characteristic tube curve, for purposes which willappear. The battery B is a filament battery for tubes 181 and 182.Battery B and battery B are filament batteries for the tubes 183-184respectively, while B and B are the plate batteries for the same. Theantenna circuit radiates at a frequency determined by the tuning of thecircuit 190, and it is to be observed that with this arrangement theradiated frequency is not the beat wave beltHl tween the incoming wavefrom antenna 185 and the frequency produced by the oscillator 182, butis the mean frequency between these two, and also that the filtercoupler 188 is tuned sharply to this frequency. In these respects, theapparatus of Fig. 8 is very different from an ordinary superheterodyneset, which invariably makes use of the heat wave. In this case the beatwave is not. taken off, but appears as an envelope on the mean frequencywhich is the carrier wave produced, amplified and radiated by themachine from the antenna 191. In other words, by heterodyning and thenamplifying and radiating the wave carrying the original modulations, Iproduce what is really a double modulated carrier wave, since the meanfrequency wave has an envelope corresponding exactly to the wave or beatfrequency between the original carrier and the heterodyning oscillatorwaves.

Referring to Fig. 9, the apparatus therein is a modifications of what isshown in Fig. 8 but using autodyne receiving tube 182 instead of twotubes shown in Fig. 8. In this case the tube 182 is said to oscillate atthe heterodyning frequency, while the circuit 186"187 is tuned to thefrequency of the incoming carrier wave. A resultant or mean frequencywave is produced, carrying the original modulations, and having anenvelope of the frequency of the beat. This wave is propagated throughthe coupler 188 into the grid circuit of the tube 183, which is thefirst amplifier tube, and from there on the operation is the same asdescribed of Fig. 8.

Referring now to Fig. 10 this is a further arrangement of apparatus andcircults for receiving on any short wave length and relaying by doublemodulation. The receiving antenna 200 is connected through coupler 201to the grid circuit of the first detector 203, the input circuit beingtuned by means of a variable condenser 202 as usual. The plate circuitof the detector 203 is connected to the tuned filter coupler 210, andthe grid or input circuit is coupled through a triple coil coupler tothe oscillator 204. The other side of the filter coupler 210 isconnected to the grid circuit of the amplifying tube 205, the platecircuit of which goes to the transformer 211, the secondary of which isconnected to the grid circuit of the amplifier tube 206, whose platecircuit is in turn connected to the transformer 212, the secondary ofwhich feeds the grid circuit of the modulator tube 207, which isconnected in a Heising transmission circuit including the oscillatortube 208, and the radiating circuit. 215. The plate circuit of theoscillator tube 207 has the usual power battery B and choke coil 213,while the oscillating circuit of the tube 208 includes the resistancecoil 214 and the tuning elements of the anditferent carrier wave.

tenna circuit. Batter B is the plate battery of the tube 203, attery Bis the filament battery, common to the tubes 203-204, and battery Btaken with the battery B in series constitutes the plate battery of theoscillator tube 204. B is the filament battery of the amplifier tubes, Bis the high voltage plate battery of the same, B is the power battery ofthe modulator oscillator circuit while battery B is a grid battery forthe oscillator tube 208. 13 is the filament battery for the same tube.

This arrangement of Fig. 10 is the same as the ordinary superheterodynecircuit up to the tube 207. According to usual practice this tube wouldbe a second detector and would be followed by one or more stages ofaudio amplification. In the present case, this tube is a modulator,which takes the beat waves passed through the tuned filter coupler 210,and amplified in the tubes 205-206, and imposes them on the highfrequency carrier current generated by the tube 208 and radiated fromthe antenna 215. This shows another method of taking a single modulatedincoming wave and by heterodyning and remodulating, sending out the sameaudio modulations unchanged on a The waves radiated from the antenna 215also require receiving instruments capable of double demodulation.

lVhat I claim is:

1. A radio receiving system comprising a plurality of primary receivingstations, a secondary receiving station, individual line wires extendingfrom said primary receiving stations to said secondary receivingstation, signal receiving and retransmitting means at the primarystations arranged to receive and retransmit signals over theirindividual lines to the secondary station, and signal receiving andretransmitting means at the secondary station arranged to beinterchangeably connected with said lines for receiving andretransmitting the same signals over any one of said lines.

2. A radio receiving system comprising a primary receiving station, asecondary receiving station, a line connecting said stations, means atsaid primary receiving station for demodulating a primary wave receivedthereat and transmitting the modulations over said line tosaid secondarystation, means at the secondary station for demodulating saidmodulations and transmitting the secondary modulations thus obtainedover the line to the primary station.

3. A radio receiving system for double modulated waves comprising aprimary re ceiving station, a secondary receiving station. a linecircuit connecting said stations, demodulating means at the primarystation for receiving the primary double modulated waves andtransmitting the intermediate frequeue waves over the line circuit tothe secondary station, and second demodulating means at the secondarystation for receiving said intermediate frequency waves and transmittingthe modulations thereof over the line circuit to the primary station.

4. A radio receiving system comprising a receiving station, a servicestation, a. line circuit connecting said stations, radio receivingapparatus partly at the receiving station and partly at the servicestation connected over said line circuit, and means for metering the useof that part which is located at the service station.

5. A radio receiving system comprising a. plurality of receivingstations, at service sta tion, line circuits connecting said receivingstations with the service station, radio receiving apparatus for partialreceiving at each receiving station, radio receiving apparatus at theservice station arranged to be interchangeably connected with theapparatus at any of the receiving stations over said line circuits tocooperate with the same to effect complete reception at the receivingstation. and means for metering the use of the service stationapparatus.

6. A radio broadcast distributing system comprising means forbroadcasting by radio on a double modulated wave, a plurality ofsubscribers stations, at service station, line circuits connecting saidsubscribers stations with the service station, radio receiving anddemodulating apparatus at each subscribers station arranged to receivethe double modulated waves, demodulate the primary wave to detect theintermediate wave and transmit the same over the line circuit to thesaid service station, and receiving and demodulating means at theservice station arranged to receive the intermediate wave transmittedover the line, demodulate the same and retransmit the signal wave backover the line to the subscribers station.

7. A radio broadcast distributing system comprising means forbroadcasting by radio on a double modulated wave, a plurality ofsubscribers stations, a service station. line circuits connecting saidsubscribers stations with the service station. radio receiving anddemodulating apparatus at each suhscribers station arranged to receivethe double modulated waves, demodulate the primary wave to detect theintermediate wave and transmit the same over the line circuit to thesaid service station, and receiving and demodulating means at theservice station arranged to receive the intermediate wave transmittedover the line, demodulate the same and retransmit the signal wave backover the line to the subscribers station.

8. A radio broadcast distributing system comprising an originatingbroadcasting station having means for broadcasting on a. doublemodulated wave, a relay broadcasting station having means for receivingsaid double modulated wave and rebroadcasting the intermediate wave on asecond carrier wave different from the first double modulated wave, aplurality of subscribers stations, aservice station, line circuitsconnecting the substations with the service station, radio receiving anddemodulating apparatus at each subscribers station arranged to receivesaid second carrier Wave, demodulate the same to detect the intermediatewave and transmit the same over the line circuit to the service station,and receiving and demodulating apparatus at the service station arrangedto receive the intermediate Wave transmitted over the line, demodulatethe same and transmit the signal wave over the line back to thesubscribers station.

9. A radio receiving system comprising a plurality of primary receivingstations, at service station, line circuits connecting said primarystations with said service station, means at the primary stations forreceiving radio signals and retransmitting the same by carrier currentover the line circuits to the service station, and means at the servicestation arranged to be interchangeably connected with any of said linecircuits for receiving the signal from the carrier wave andretransmitting the signal over the line circuit to the same primarystation.

10. A radio receiving system comprising a plurality of subscribersstations, a service station, line circuits connecting said subscribersstations and the service station, means at each subscribers station forreceiving radio signals and retransmitting the same over the linecircuit on a carrier current of given frequency, means at eachsubscribers station for tuning the line circuit, and means at theservice station adapted to be connected with any of said line circuitsfor tuning the line, receiving the signal borne by said given carriercurrent and retransmitting the signal over the line to the subscribersstation.

11. In a telephone exchange system having subscribers lines terminatingin multiple connection terminals, and link circuits for interconnectingsaid lines through said terminals; the combination therewith of ademodulating apparatus arranged to be connected with any of said linesthrough said multiple connecting terminals.

12. In a telephone exchange system having a plurality of subscriberslines terminating in multiple connecting terminals, link circuits forinterconnecting said lines through said terminals, a meter circuit foreach line having multiple connecting terminals associated with said lineconnecting terminals, and means associated with said link circuits forenergizing said meter circuits; the combination therewith of ademodulating circuit arranged to be connected with any of said linesthrough said multiple connecting terminals and means associated withsaid domodulating circuit for energizing said meter circuit.

13. A radio receiving system comprising a receiving stat-ion, a servicestation, aline circuit connecting said stations, radio receivingapparatus consisting of parts at the receiving station, the line circuitand interchangeable parts at the service station, and means for'difi'erentially metering the use of said different interchangeableparts according to the quality of service given by them.

14. A radio broadcast distributing system comprising means forbroadcasting on a double modulated wave, a receiving station, a servicestation, a line circuit connecting said stations, apparatus at thereceiving station for partly demodulating said wave, a plurality ofdemodulating apparatus at the service staiton arranged to beinterchangeably connected through said line with said demodulatingapparatus at the receiving station to complete the demodulation andtransmit the signal over the line to the receiving stationat difi'erentdegrees of volume according to the particular service station apparatusused, and means for differentially metering the use of different ones ofsaid service station apparatus.

15. In a telephone exchange system having a plurality of subscriberslines terminating in multiple connecting terminals. link' circuits forinterconnecting said lines through said terminals, a meter circuit foreach line having multiple connecting terminals associated with said lineconnecting terminals, and means associated with said link circuits forenergizing said meter circuits; the combination therewith of adelnodulating circuit arranged to be connected with any of said linesthrough said multiple connecting terminals and means associated withsaid demodulating circuit for energizing said meter circuitperiodically.

16. A combined radio and wire system of broadcast distributioncomprising a plurality of subscribers stations divided into groups, asubscribers radio service station for each group, radio receiving meansat each subscribers station having wire connection with its groupservice station, a master radio broadcast station, and intermediaterelay stations, means at said master, intermediate and service stationsfor transmitting a signal-modulated intermediate frequency wave from themaster station through the relay and service stat-ions to the radioreceiving means at the subscribers stations, said subscribers receivingapparatus being arranged to relay said intermediate frequencyreflectively back to its service station over the wire connection andmeans at said service station for demodulating said wire transmittedintermediate frequency wave to obtain the original signal wave andretransmit the signal back over the wired connection to the subscribersstation. whereby only persons connected with both wired and radiosystems will receive the said signals.

17 In a. telephone exchange system, a central station, a plurality ofsubscribers lines terminating at the central station, a meter for eachsubscribers line at the central station, different apparatus elements atthe central station arranged to be interchangeably connected with thesubscribers line terminals according to different kinds of service to berendered a subscriber, and means associated with said difi'erentapparatus element-s operable upon connection of its apparatus elementwith a line to differentially actuate the meter of said line accordingto the apparatus used.

In testimony whereof I hereunto afiix my signature.

EDWARD E. CLEMENT.

